Fig. 1

(a) Schematic representation of the self-alignment kinematic chain of the I-Phlex exoskeleton. The mechanism is based on an RPR configuration, in which the first rotational joint is composed by a series of hinges. In the upper figure the rotational-prismatic-rotational joints are highlighted; in the lower figure, the self-alignment chain is depicted in the ‘zero position’ and the geometric parameters used the model are indicated. (b) Overview of the I-Phlex exoskeleton system worn by a user. The main components are highlighted. (b) Overview of the control algorithm for the platform operation. The HLCL is devoted to the estimation of the anatomical parameter of interest, i.e. the MCP angle \(\:{\theta\:}_{est}^{MCP}\). In the same layer, the user can select among different exercises through the exoskeleton GUI, which in turn determines the reference trajectory for the user \(\:{\theta\:}_{des}^{MCP}\). The rehabilitation paradigms are rendered in the MLCL by exploiting the impedance control strategy and modifying the controller gain according to the selected exercise modality (passive or active-assistive). Within the same layer, the reference torque trajectory (\(\:{\tau\:}_{des}^{MCP}\)) for the LLCL is translated from the anatomical workspace to the robot once by exploiting an inverse kineto-static model (IKsM), implemented using patient-specific LUT. Finally, the LLCL is devoted to driving the actuation unit to apply the desired torque at the joint level, closing the loop on the measured torque from the SEA (\(\:{\tau\:}_{meas}^{SEA}\))